1. Field of the Invention
The present invention relates to a cast-in concrete, lead-in system for ceilings and walls having a trapezoidally corrugated sheet metal framework and including a lead-in sleeve for receiving one of a tubular conduit and a cable and having at least three outer, circumferentially spaced from each other, fixing points for securing the lead-in sleeve to the trapezoidally corrugated sheet metal formwork.
2. Description of the Prior Art
In contemporary building constructions, formworks formed of trapezoidally corrugated sheet metal that consists of alternating valley and peak regions, found a wide application. Primarily, such formworks are used in substantially horizontal ceilings and are cast in concrete on the site. The trapezoidally corrugated sheet metal remains on the lower side of the ceiling. Often, for subsequent insertion of tubular leads-in through the ceiling, space retainers are mounted in the formwork to provide a concrete-free space for the leads-in.
Likewise, space retainers are provided in double walls. The space retainers for conduits or cable leads-in, before being cast-in concrete, should be reliably secured both axially and angularly with respect to the formwork plane.
U.S. Pat No. 4,261,598 discloses mounting on a formwork of a coupling sleeve instead of a cast-in concrete, space retainer, and a tubular member having a tubular end, which partially projects into the coupling sleeve, and extends through an opening formed in the formwork.
U.S. Pat. No. 4,669,759 discloses fire-retarding leads-in which include an appropriately deformed lead-in sleeve, an end-side outer ring for a temporary mounting, and a ring-shaped sealing which is partially formed of an intermescent material and is mounted inside the lead-in sleeve in the radially widen region of the sleeve. The lead-in is mounted on the formwork and is cast in concrete.
U.S. Pat. No. 5,293,724 discloses a short mounting sleeve with an end surface outer ring for mounting the sleeve on a trapezoidally corrugated sheet metal, and a tubular member extending through the sleeve, the formwork and the concrete ceiling. The end surface outer ring is mounted either in a valley region, on a peak region, or is mounted over two adjacent peak regions. The drawback of this solution consists in that this non-fire-retarding mounting sleeve is characterized by a limited mountability with respect to different, conventionally used formworks because of the difficulty to proper dimension the outer ring. A reliable mounting of such leads-in, in particular of leads-in having small diameters, with respect to precise positioning of the lead-in, is not always possible because of different widths of peak and valley regions of the trapezoidal corrugations of the sheet metal. In the transitional region between peak and valley regions or in a valley region adjacent to the transitional region, a securing of a lead-in is not possible at all or, maximum, a one-sided attachment is possible. Such an attachment, of course, cannot provide a reliable attachment for a subsequent concrete cast-over.
Accordingly, an object of the present invention is to provide a lead-in system for ceilings and walls having a trapezoidally corrugated sheet metal formwork, which can be reliability secured in all positions on all conventional trapezoidally corrugated sheet metal formworks.
Another object of the present invention is to provide a reliably securable fire-retarding lead-in system.